demux_disc: pass seek flags to stream layer

Pass through the seek flags to the stream layer. The STREAM_CTRL
semantics become a bit awkward, but that's still the least awkward
part about optical disc media.

Make demux_disc.c request relative seeks. Now the player will use
relative seeks if the user sends relative seek commands, and the
demuxer announces it wants these by setting rel_seeks to true. This
change probably changes seek behavior for dvd, dvdnav, bluray, cdda,
and possibly makes seeking useless if the demuxer-cache is set to
a high value.

Will be used in the next commit. (Split to make reverting the next
commit easier.)

4 files changed, 21 insertions, 9 deletions

diff --git a/demux/demux.c b/demux/demux.c
index c099dbac19..51131dfd4c 100644
--- a/demux/demux.c
+++ b/demux/demux.c
@@ -760,6 +760,7 @@ static void demux_copy(struct demuxer *dst, struct demuxer *src)
         dst->seekable = src->seekable;
         dst->filetype = src->filetype;
         dst->ts_resets_possible = src->ts_resets_possible;
+        dst->rel_seeks = src->rel_seeks;
         dst->start_time = src->start_time;
     }
     if (src->events & DEMUX_EVENT_STREAMS) {
diff --git a/demux/demux.h b/demux/demux.h
index ca96d60732..b53a30c805 100644
--- a/demux/demux.h
+++ b/demux/demux.h
@@ -71,11 +71,12 @@ struct demux_ctrl_stream_ctrl {
     int res;
 };
 
-#define SEEK_ABSOLUTE (1 << 0)
-#define SEEK_FACTOR   (1 << 1)
-#define SEEK_FORWARD  (1 << 2)
-#define SEEK_BACKWARD (1 << 3)
-#define SEEK_SUBPREROLL (1 << 4)
+#define SEEK_ABSOLUTE (1 << 0)      // argument is a timestamp
+#define SEEK_FACTOR   (1 << 1)      // argument is in range [0,1]
+#define SEEK_FORWARD  (1 << 2)      // prefer later time if not exact
+#define SEEK_BACKWARD (1 << 3)      // prefer earlier time if not exact
+#define SEEK_SUBPREROLL (1 << 4)    // try to get more subtitle packets
+#define SEEK_HR       (1 << 5)      // hr-seek (this is a weak hint only)
 
 // Strictness of the demuxer open format check.
 // demux.c will try by default: NORMAL, UNSAFE (in this order)
@@ -188,6 +189,9 @@ typedef struct demuxer {
     double start_time;
     // File format allows PTS resets (even if the current file is without)
     bool ts_resets_possible;
+    // Send relative seek requests, instead of SEEK_ABSOLUTE or SEEK_FACTOR.
+    // This is only done if the user explicitly uses a relative seek.
+    bool rel_seeks;
 
     // Bitmask of DEMUX_EVENT_*
     int events;
diff --git a/demux/demux_disc.c b/demux/demux_disc.c
index 69643a0053..37b189861f 100644
--- a/demux/demux_disc.c
+++ b/demux/demux_disc.c
@@ -169,6 +169,7 @@ static void d_seek(demuxer_t *demuxer, double rel_seek_secs, int flags)
     double pts = p->seek_pts;
     if (flags & SEEK_ABSOLUTE)
         pts = 0.0f;
+    double base_pts = pts; // to what pts is relative
 
     if (flags & SEEK_FACTOR) {
         double tmp = 0;
@@ -180,7 +181,8 @@ static void d_seek(demuxer_t *demuxer, double rel_seek_secs, int flags)
 
     MP_VERBOSE(demuxer, "seek to: %f\n", pts);
 
-    stream_control(demuxer->stream, STREAM_CTRL_SEEK_TO_TIME, &pts);
+    double seek_arg[] = {pts, base_pts, flags};
+    stream_control(demuxer->stream, STREAM_CTRL_SEEK_TO_TIME, seek_arg);
     demux_control(p->slave, DEMUXER_CTRL_RESYNC, NULL);
 
     p->seek_pts = pts;
@@ -312,6 +314,8 @@ static int d_open(demuxer_t *demuxer, enum demux_check check)
     // Can be seekable even if the stream isn't.
     demuxer->seekable = true;
 
+    demuxer->rel_seeks = true;
+
     // With cache enabled, the stream can be seekable. This causes demux_lavf.c
     // (actually libavformat/mpegts.c) to seek sometimes when reading a packet.
     // It does this to seek back a bit in case the current file position points
diff --git a/player/playloop.c b/player/playloop.c
index cabdb4e441..bcec02e21a 100644
--- a/player/playloop.c
+++ b/player/playloop.c
@@ -204,7 +204,7 @@ static int mp_seek(MPContext *mpctx, struct seek_params seek,
         }
     }
     int direction = 0;
-    if (seek.type == MPSEEK_RELATIVE) {
+    if (seek.type == MPSEEK_RELATIVE && (!mpctx->demuxer->rel_seeks || hr_seek)) {
         seek.type = MPSEEK_ABSOLUTE;
         direction = seek.amount > 0 ? 1 : -1;
         seek.amount += get_current_time(mpctx);
@@ -233,10 +233,13 @@ static int mp_seek(MPContext *mpctx, struct seek_params seek,
         demuxer_style |= SEEK_ABSOLUTE;
         break;
     }
-    if (hr_seek || direction < 0)
+    if (hr_seek || direction < 0) {
         demuxer_style |= SEEK_BACKWARD;
-    else if (direction > 0)
+    } else if (direction > 0) {
         demuxer_style |= SEEK_FORWARD;
+    }
+    if (hr_seek)
+        demuxer_style |= SEEK_HR;
     if (hr_seek || opts->mkv_subtitle_preroll)
         demuxer_style |= SEEK_SUBPREROLL;